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From: | Thomas Parrott |
Subject: | Re: Fwd: Adding devices via QMP's device_add don't have their bootindex setting respected |
Date: | Tue, 18 May 2021 14:08:22 +0100 |
On 18/05/21 14:22, Thomas Parrott wrote:
> Due to QEMU moving towards a QMP configuration mechanism and away from
> config file support, the LXD team are currently in the process of
> migrating to using QMP to add devices to VMs (so that we can support the
> use of QEMU 6.0).
If the only issue you have is with -spice, that's just a bug that we
need to fix. -readconfig is still supposed to work, even though
-writeconfig is deprecated and I'd like to remove it as soon as 6.1.
In particular, the issue you reported below is not a bug. Devices that
are added after startup are considered hotplugged, and the boot index
list is frozen until the next reset. QMP-based configuration of
coldplugged devices is in the works, but unfortunately it is not yet ready.
Paolo
> Currently we are using the `-S` flag to freeze CPU at startup, then
> using QMP to add NIC devices via the `device_add` command, and then
> using the `cont` command to start the VM guest.
>
> This is working mostly fine, but there is one issue; the provided
> "bootindex" property is not respected.
>
> E.g.
>
> device_add
> {"addr":"00.0","bootindex":"0","bus":"qemu_pcie4","driver":"virtio-net-pci","id":"dev-lxd_eth0","mac":"00:16:3e:0c:69:e7","mq":"on","multifunction":"off","netdev":"lxd_eth0","vectors":"6"}
>
> The device is seen within the VM guest and the VM BIOS, but its boot
> order is last rather than first.
>
> We've also tried using a non-zero bootindex of 1 and that has the same
> effect.
>
> After discussions on #qemu IRC channel, we found that running
> `system_reset` after adding the devices allowed the `bootindex` property
> to be respected.
>
> So this looks like bug. Perhaps we can discuss it in one of the
> forthcoming community calls?
>
> Thanks
> Tom Parrott
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